1. Field of the Invention
The invention relates to rolling, and more particularly, to mill stand roll assembly.
The mill stand roll assembly of the invention is readily adaptable for use in section and wire rolling mills.
The invention may also find application in other industries where accurate adjustment of the mutual disposition of two rolls is essential, as, in disk shears for maintaining a specified mutual disposition of disk shears, and also in devices where a shaft is to be held axially fixed when acted upon by an axial load.
2. Description of the Prior Art
There is widely known a mill stand roll assembly comprising two grooved rolls with roll passes on their surfaces. The rolls are set in a parallel relationship with one another and are intended for passing therebetween billets to be rolled.
Each of the rolls has end necks coaxial with the roll, and the free end of each of the necks having a thrust shoulder.
Each thrust shoulder is placed in a double-sided hydrostatic bearing disposed in a chock serving as a housing for said bearing and secured in the housing of the mill stand.
The hydrostatic bearing is provided with thrust disks, each being arranged at both end faces of each thrust shoulder substantially in parallel to said end faces. The thrust disks, the thrust shoulders and the chocks form cavities which communicate with a source of lubricant through a hole in the chock.
These cavities are intended to receive a liquid under pressure from the source of lubricant and to provide in the gap between the thrust disk and the thrust shoulder a hydrostatic pressure field balancing an axial load applied to the thrust shoulder.
The known roll assembly is provided with a liquid source of constant delivery, communicating with the cavities of the hydrostatic bearings.
The mutual disposition of the grooved rolls in the known roll assembly, i.e. the accuracy of alignment of roll grooves, is determined by the mutual disposition of the thrust shoulders with respect to the mill stand housing, said shoulders being adjusted by setting the thrust bearings as required with respect to the housing.
However, the rolls tend to displace in the course of rolling one relative to another within the range of gaps and deformations of the thrust bearings.
These roll displacements may be caused by inaccuracies in the profile of items rolled in the preceding mill stand or by irregularities in the mechanical properties of items being rolled or by any other causes.
Such displacements are governed by the amount of axial force applied to the rolls and by the rigidity of the hydrostatic bearings, which is determined mainly by the hydraulic resistance of the elements supplying the liquid under pressure to the hydrostatic bearings.
The displacement of the rolls affects the mutual arrangement of the roll grooves and thus results in poor accuracy of the manufactured items.
Furthermore, the displacement of the rolls changes the sizes of the gaps between the thrust shoulders and the disks, or more specifically, decreases the gap between the thrust shoulder and the disks loaded by pressure, as well as increases the gap between the thrust shoulder and the non-loaded disk. Because of this, the disk taking up the load is render more severe service conditions than the non-loaded disk.
The mutual disposition of the rolls in the known mill stand roll assembly is adjusted with the aid of a known device, this necessitating stopping of the mill and thus lowering mill efficiency.